Turkey's foreign minister says his government has agreed in "principle" with the United States to provide air protection to Syrian rebels being trained to fight Islamic State militants in Syria.

Mevlut Cavusoglu told Turkish media in comments published Monday that without air support, the training program announced by Turkey and the United States to prepare moderate opposition members in the country for battle would be pointless.

Also Monday, a U.S. defense official told VOA that Washington was in "ongoing discussions" with Ankara but that "no decisions have been made."

Ankara has been reluctant to dispatch any military power across its borders in the conflict.

Meanwhile, Syrian government forces carried out at least 15 airstrikes Monday targeting Islamic State fighters in the central city of Palmyra, activists said.

The Britain-based Syrian Observatory for Human Rights, which monitors violence in Syria through a network of people inside the country, said the targets included a military intelligence building and a hospital.

The Islamic State group seized the historic city last week.

The Observatory said the militants have executed 217 people, including children, nurses and Syrian forces, and that more than 600 people have been taken prisoner.

Observatory director Rami Abdel Rahman told the French News Agency that some of those executed were beheaded, while others were shot or stabbed. The observatory said Islamic State accused those killed or captured of being Syrian "regime agents."

Syrian state media said more than 400 people have been killed.

In addition to the human toll, the presence of Islamic State fighters in Palmyra raises fears about the fate of 2,000-year-old Roman ruins that are listed among UNESCO's World Heritage sites.

The Islamic State group has a history of destroying monuments and statues the extremists regard as blasphemous.